1. Technical Field
The inventive arrangements relate generally to methods and apparatus providing advanced operating features for video only and both video and audio programs recorded on disk media, for example recordable digital video disks, hard drives and magneto optical disks.
2. Description of the Related Art
Various devices have been developed to enable consumers to record video and/or audio programs for later presentation. Such devices include tape recorders, video cassette recorders, recordable compact discs, and most recently, recordable digital video discs (DVD). Hard drives and magneto optical discs have also been used.
A DVD that can be recorded on only once, and thereafter is essentially a DVD read only memory, is referred to by the acronym DVD-R. The acronym DVD-R is also used generally to refer to the write-once, or record-once, technology. Several formats are available for DVD's to be recorded on, erased and re-recorded; that is, overwritten or rewritten. These are referred to by the acronyms DVD-RAM, DVD-RW and DVD+RW. As of this time no uniform industry standard has been adopted. The acronyms DVD-RAM, DVD-RW and DVD+RW are also used generally to refer to the respective rewritable technologies. Reference herein to rewritable DVD technology, devices and methods is generally intended to encompass all of the standards which are now being used, as well as those which may be developed in the future.
A DVD recorder has the capability to record video onto a disc medium and playback the video at different speeds. For example, a DVD recorder can playback video at fast-forward or slow-motion speed. In addition, a DVD recorder can pause the video to display a single image from the recorded video. These playback variations are commonly referred to as trick modes. Typically, a DVD recorder performs these trick modes by repeating one or more pictures contained in the recorded video. For example, a DVD recorder can repeat every picture from a particular portion of recorded video to give the viewer the impression that the video is being displayed at one-half its normal speed. In the fast-forward trick mode, the DVD recorder can repeat one or more pictures from the video and then skip a plurality of pictures before repeating the next set of pictures. If the video is paused, the DVD recorder can continuously repeat the same picture that was last displayed when the pause command was received.
A DVD recorder can play recorded video on televisions that use either an interlaced scanning format or a progressive scanning format. Under the interlaced scanning format, the video picture signal is typically divided into 525 horizontal lines. During each field period, however, only one-half of these lines are scanned; the odd-numbered lines are scanned first, and the even-numbered lines are scanned thereafter. Each sweep is referred to as a field, and when combined, the two fields form a complete picture or frame. For an NTSC system, sixty fields are displayed per second, resulting in a rate of thirty frames per second.
Under the progressive scanning format, each of the horizontal lines of the video picture signal is scanned during each picture sweep. Thus, the entire picture is displayed after a particular picture sweep. Although the scanning rate in a progressive scanning format must be doubled as compared to the rate in an interlaced format, progressive scanning produces a superior picture. As a result, the progressive scanning format has been adopted in a number of high performance media devices such as computer monitors and some high-definition televisions (HDTV).
In certain DVD recording systems, it may be desirable to decode the outgoing video signal, typically an MPEG formatted signal, at a location external to the DVD recorder. For example, in a number of these systems, the MPEG decoder is located in the television on which the recorded video is being played back. Bypassing the decoding system of the DVD recorder is typically done if the viewer wishes to playback video on an ATSC television such as HDTV. HDTV televisions require high bit rates and as a result, must have decoders that can decode complex video signals. These decoders can be expensive and generally are not included in many of today's recordable DVD devices. Accordingly, many manufacturers of HDTV televisions implement into their HDTV televisions MPEG decoders capable of decoding high bit rate MPEG signals.
Under this arrangement, however, artifacts may appear in the video display of the HDTV television during trick mode playback of video recorded under an interlaced format. This problem is prevalent in HDTV televisions that can perform either progressive scanning, interlaced scanning or a combination thereof. One example of such an artifact is a vibration effect that is produced when video containing a moving object is recorded and played back under trick mode on such a television.
As a moving object moves across the screen in an interlaced scan television, each field will only display a portion of the moving object. This is because a field only displays every other horizontal line of the overall picture. For example, for a particular field n, only the odd-numbered horizontal lines are scanned and the portion of the moving object that will be displayed in field n is the portion that is scanned during the odd-numbered horizontal line sweep for field n. The next field, field n+1, is created 1/60 of a second later and will display the even-numbered horizontal lines of the picture. Thus, the portion of the moving object that is displayed in field n+1 is the portion that is scanned during the even-numbered horizontal line sweep for field n+1. Although each field is temporally distinct, the human eye perceives the sequential display of the fields as smooth motion due to the speed at which the fields are displayed.
As a DVD recorder records video being displayed in the interlaced format, each frame is recorded onto a particular disc medium. During playback, these frames can be sent to the remotely located television for decoding and display. Since progressive scan televisions are designed to display complete frames, these televisions are typically equipped with a deinterlacer. When complete frames are sent to the television, the frames are decoded and the interlaced fields that constitute the complete frames are separated. Once these fields are separated, the television instructs its deinterlacer to deinterlace each field. Deinterlacing each interlaced field comprising the frames results in an overall higher picture quality.
If the viewer activates any of the trick modes, the video signal sent from the DVD recorder to the progressive scan television will contain repeated frames from the video recorded under the interlaced format. As an example, if the viewer pauses the video to display a single frame, the DVD recorder will continuously send the same frame for display on the progressive scan television. Subsequently, the fields that constitute the particular frame being repeated are deinterlaced to form two separate frames. Accordingly, the progressive scan television will alternately display the frames created by the deinterlacing process.
As noted earlier, if a moving object appears in the video recorded under the interlaced format, each field will only display a portion of the moving object. Thus, as the frames constructed from the deinterlaced fields are alternately displayed in a repeated fashion, the moving objects in the display appear to vibrate during the trick mode. This is because the frames created by deinterlacing each interlaced field are temporally distinct, and the moving object appears in a different position for each frame. As the television alternately displays these two frames repeatedly during the trick mode, the moving object appears to vibrate resulting in an unwanted artifact.
This vibration effect appears in the fast-forward and slow-motion trick modes as well. In fact, any playback process that utilizes repeating pictures that contain moving objects produces this artifact. Moreover, this artifact is not limited to televisions that only employ the progressive scanning format; ATSC televisions that have the capability to display either interlaced or progressive signals, such as an HDTV that displays a 1080 line interlaced signal, also suffer from this drawback. As a result, it is desirable to eliminate this artifact without any significant change in the hardware of the DVD recorder system and without any increase in costs.